Police in Nepal's capital broke up at least two protests by Tibetan refugees, monks and their supporters Monday and arrested about 475 people, the United Nations said.

The U.N.'s human rights office in Nepal said the arrested included some prominent Nepali human rights activists who joined the protests.

A demonstration in the morning near the U.N. offices in Katmandu by 200 Tibetan refugees and monks was broken up by police, who beat them with bamboo sticks and arrested scores.

Even before the protest began, police detained people who were either on their way to the area or gathering for the demonstration.

Police official Sarad Karki said about 245 were arrested in the Lalitpur area, where the U.N. offices are located. The number included those arrested during the protest and those who were detained while heading to the venue.

The protesters demanded the U.N. investigate the recent crackdown in Tibet by Chinese authorities.

Chanting "China, stop killings in Tibet. U.N., we want justice," the protesters were marching toward the U.N. offices when police stopped them about 100 meters (300 feet) away and snatched their banners.

When the Tibetans tried to break through the police line and push ahead, officers charged with batons and arrested scores of people, dragging them to trucks and vans to be taken to police stations.

The second protest near Singhadurbar, where the prime minister's office and all government ministries are located, was also stopped by police, but less force was used.

Police official Sarvendra Khanal said 155 protesters were arrested.

The officials could not explain why the U.N. said 475 were arrested while police said only 400.

The U.N. human rights office said it was "deeply concerned at the arbitrary arrests and detentions of several hundred individuals."

"These actions by police violate individuals' basic rights to freedom from arbitrary detention and freedom of movement, in addition to impairing the individuals' rights to peaceful assembly and expression," the U.N. said in a statement.

Nepal has said it will not allow protests against any "friendly nation," including China.

International human rights groups and the U.N. have already criticized Nepal over its use of force in the past several days against protests in Katmandu involving some of the thousands of Tibetan refugees living in the country.

New York-based Human Rights Watch also urged Nepal to stop doing "Beijing's bidding" and end its crackdown on Tibetan exiles protesting against China.

The group said last week Nepal "should cease arbitrary arrests and detentions, harassment, and the use of excessive force to silence Tibetan protesters, activists and journalists."

Nepal's government has good relations with neighboring China, and has not issued any statements on Beijing's crackdown on anti-Chinese protests in Tibet.

Nepal's border with China in the Himalayas is a key route for Tibetans fleeing Chinese rule in the region.

Thousands of Tibetan refugees live with relatives in Nepal or in camps funded by aid groups. Most of the refugees eventually move to India, where Tibet's government-in-exile and its spiritual leader, the Dalai Lama, are based.